Conventionally, various radiation imaging devices that cause an object to transmit a radiation and images an internal structure of the object are devised. A general radiation imaging device captures a projection image of a radiation by applying the radiation to an object and causing the object to transmit the radiation. A variation in density appears in such a projection image in proportion to a radiation transmission level and represents an internal structure of the object.
Such a radiation imaging device can capture an image of only an object having characteristics of absorbing a radiation to some extent. For example, a biological soft tissue may absorb almost no radiation, or may have almost no absorption difference from surrounding substances. Even if a general device captures an image of such a tissue, almost nothing will be reflected in the projection image. Thus, imaging an internal structure of an object having no radiation absorption difference with a general radiation imaging device is theoretically limited.
Therefore, a radiation phase contrast imaging device that images an internal structure of an object by using a phase change of a transmitted radiation has been devised. Such a device images an internal structure of an object by using Talbot interference (for example, refer to Patent Literature 1).
FIG. 21 describes a radiation phase contrast imaging device. The radiation phase contrast imaging device includes a radiation source 53a that emits a radiation, a multi-slit 53b that makes a phase of the radiation uniform, a phase grating 55 having a bamboo blind-shaped pattern, and a detector that detects the radiation. The device of FIG. 21 has a configuration in which a subject is placed at a position sandwiched between the phase grating 55 and the detector. The multi-slit 53b has a configuration in which slits extending vertically are arranged laterally. The phase grating 55 has a configuration in which longitudinally extending shielding wires that do not easily transmit the radiation are arranged laterally.
A principle of the radiation phase contrast imaging device will be briefly described. When a radiation is emitted to the phase grating 55, a self-image of the phase grating 55 appears at a position distant from the phase grating 55 by a specified distance (Talbot distance). A position of the detector with respect to the phase grating 55 is adjusted such that this self-image is reflected. This self-image is an image that looks like a shadow of the phase grating 55 reflected. However, it is to be noted that the self-image is an interference fringe generated by radiation interference, and is not a mere projection.
When the subject is installed between the phase grating 55 and the detector, the radiation emitted from the phase grating 55 is transmitted through the subject before being detected by the detector. The self-image that appears on the detector at this time is slightly disturbed by being transmitted through the subject. This disturbance results from a phase shift while the radiation is transmitted through the subject.